1. Field of the Invention
The present invention relates to an ultrasonic measuring device, especially to an ultrasonic measuring device for measuring the thickness of a large flat plate.
2. Description of Prior Art
Oil tanks are critically important equipment for the petrochemical industry. Usually they are used to store petroleum or petroleum products. They can range in volume from several gallons to millions of barrels.
Large oil tanks are mostly situated on soil or specially treated ground. Due to dirt, water, and other impurities that rest at the bottom of tanks, the upper side of the steel plates at the bottom of the tanks rusts continuously. On the outside, ground water and rainwater wear down the lower side of the plates so that pitting and rusting develop. When the steel plates rust through, oil or petroleum will leak and pollute the environment. Therefore, measuring the residual depth (thickness) of the bottom plates of oil tanks is very important.
The upper side of the bottom plates can be visually inspected after oil contents of the tank are discharged. However, the lower side of the bottom plates cannot be so inspected. Usually this is done by ultrasonic equipment. However, the procedure involves some difficulties, including:
1) When the upper and lower sides of the bottom plates are seriously corroded, conventional ultrasonic probes cannot couple with the plates well, or PA1 2) When the area of the bottom plates is too large to be inspected point by point within a short period of time.
As a result, inspections cannot be practiced routinely. Therefore, leakage by accident happens sometimes. The pursuit of a better method to inspect flat panel tank bottom is important today.